Liquid-liquid treating process



Jan. 31, 1956 w. M. BASCH 2,733,187

I IQUID-LIQUID TREATING PROCESS Filed March 19, 1952 DISTILLATIOH'Zoura.

TREATING;

Zone 1 Mai hi2. @asc B o'Jm/enbor' Clboorrzeg United States Pate2,733,187 "LIQUID-LIQUID TREATING'PROCESS Application March 19, 1952,Serial No. '27 7 ,508

.1 Claim. .(Cl..196.14.42)

The present invention is concerned with an improved process for theproduction -of high quality lubricating oils. The invention is -moreparticularly directed toward an improved liquid-liquid contactingprocess wherein .solvents having a preferential "selectivity for'themore aromatic type constituents are utilized for the treatment of oilfractions. In accordance with the present invention, solvents of thischaracter, as for example, phenol, are .efliciently recovered byutilizing a partial crystallization operation in conjunction with adistillation operation.

It is well known in the art to contact hydrocarbon fractions withsolvents having a preferential .selectivity for the more aromatic typeof hydrocarbon constituents as compared to the more paraffinic typehydrocarbon constituents. Solvents of this character are for example,phenols, .furfural, .sulfur dioxide, ..nitrobenzene, aniline, cresols,chlorex, dimethylformamide, dipropionitriles, ammonia, amines, etc. Itis also known in the art to use in conjunction with these aromatic typesolvents, solvent-modifying agents as for example, water, alcohols,esters and the like. Temperatures usually employed in the treatingoperations are in the range from about 40 F. to 250 F., while thesolvent to oil ratios are in the range from about 0.4 to volumes ofsolvent per volume of oil. These operations have been carried out eitherin batch or in countercurrent treating zone processes.

While the solvent treating operations, as described and known in theart, have been entirely satisfactory for segregating the desiredfractions and for improving the viscosity index and other criticalfactors of oils such as lubricating oil and the like by the removal ofaromatic type constituents, certain difiiculties have been encountered.For instance, it has been relatively difficult and expensive to separatethe solvent from the rafilnate phase and from the solvent extract phase.While distillation is a conventional procedure, other methods have beensuggested. Cooling of the respective phases has been utilized toseparate a solvent-rich phase which is returned to the treating zone.This is not particularly desirable since not only does the solvent-richphase contain a considerable amount of oil but also this retained oil isof a relatively high aromaticity content which is not suitable forreturning to the treating zone.

In accordance with the present invention, the phases, particularly thesolvent extract phase, is cooled to crystallize the solvent such asphenol. The crystallized phenol is separated from the liquid phase,preferably under pressure. A very desirable mode of operation is tofilter the crystallized phenol or equivalent solvent from the oil, thento press the crystals to remove oil therefrom followed by reheating andrecycling of the phenol to the treating zone. Phenol separated bydistillation is returned to the treating zone at a point above the pointof introduction of the phenol segregated by crystallization.

The process of the present invention may be readily understood byreference to the attached drawing illustrating embodiments of the same.Referring specifically to the figure,

a lubricating oil fraction is introduced into the bottom ofcountercurrent treating zone 1 'by means of line 2. An aromatic typesolvent, preferably a phenol, is introduced into 'the'top of'countercurrentitreating zone 1 by means of line 40. In accordance with.the procedure of the present invention, phenol secured as hereinafterdescribed "is introduced into treating zone 1 .at a point below thepoint of introduction of the pure vphenolsby means of'line 3. Thequantity of phenol used 'i'o1,;1mrposes of illustration is in :the rangefrom about 0.4 .to 3 volumes of phenol per volume of oil. Temperatureconditions in the countercurrent treating tower are in the range fromabout 1'1'0 F. to 250 F. 'It is preferred that the top temperature be inthe range "from about 130 F. to 250 F., while the temperature attheb'ottom of the tower be in the 'range from about 110 -F.' to 210F. Araffinate phase comprising phenol and parafi'inic'type constituents isremoved overhead from zone 1 *bymean's of line 4 andpassedtoadistillationzone 5. Temperature and pressure conditions indistillation zone 5 area'dapted to remove overhead by .means iof line 6phenol which is preferably recycled to line 40. A high qualitylubricating oil product is removed from the bottom of .distillation zone5 by means of line 8.

A solvent extractphase is removed from the bottom of extraction zone 1by means of line 9 and passed to :a

chilling zone 10. Temperattute and pressure conditions in zone-10 areadapted to precipitate thephenol. The phenol is removed from chillingzone 10 by means of line 41 and introduced into a filtering zone 42.In-zone '42 the precipitated crystals are separated from the liquidphase whichis removed from zone 42 by means of line 43. Thisliquidphasefis introduced into a distillation zone 13.

Temperature and pressure conditions in zone :13 are adapted to removeoverhead by means 70f line '14 the phenol which is preferably recycledto the system by means of line 40. A solvent-free extract oil is removedby means of line 15 and handled or further refined as desired. It is tobe understood that zones 1, 5, 10, 42 and 13 may comprise any suitablenumber and arrangement of stages.

The solvent crystals removed from zone 42 by means i of line 44 arepreferably passed to a pressing zone 45. In this zone the crystals arepressed to remove oil which is passed to distillation zone 13 by meansof lines 46 and 43. The solvent crystals are removed from zone 45 bymeans of line 47, heated in zone 48 and recycled to zone 1 by means ofline 3.

The present invention is broadly concerned with an improved solventtreating operation wherein the solvent is efficiently recovered from thesegregated phases. The method broadly comprises cooling the phase toprecipitate the solvent which is separated from the liquid phase byfilters, centrifuges or the like. It is preferred that the segregatedcrystals be then subjected to pressure in order to remove remainingtraces of the oil. The pressed crystals are reheated and recycled to thesystem at a point below the point of introduction of the solvent whichhas been segregated by distillation.

The invention is particularly applicable in the handling of a phenolsolvent wherein the water content of the solvent is maintained belowabout 4%, preferably less than about 2% by volume based upon the phenol.It is preferred that the solvent extract phase be chilled to atemperature below about 100 F., preferably to a temperature in the rangefrom about 65 to F. It is also preferred that the crystals be subjectedto a pressure in excess of 50 to lbs. per square inch. Operatingconditions should be adjusted to secure a solvent extract phase havingan oil content less than about 8%, preferably having an oil content lessthan about 5%. Under these conditions, by the procedure of the presentinvention 40 to 60% of the solvent is recovered by the procedure out- 3lined, thus reducing the load on distillation equipment by about 50%.The process of the present invention may be more fully understood by thefollowing example illustrating the same.

was solvent extracted. The temperature employed at the top of the zonewas 140 F., while the bottom temperature was 130 F. About 1.4 volumes ofphenol per volume of oil was used. In one operation the phenol had awater content of 7%, while in the second operation the water content ofthe phenol was 0.5%. The data on the solvent extract phase from therespective operations were as follows:

Recovery of crystallized phenol from phenolic extract llsmg press Phenolin Extract, Vol. Percent G9 65 B in Phenol, Vol. Percent 7 0. PressingTemperature, F 55 81 Results alter Pressing:

Phenol Content of Filtrate 47 Phenol Melting Point, F 101 104 Phenol OllContent, Vol. Percent. 1O 4 Percent Recovery of Phenol G6 83 From theabove it is apparent that the phenol secured from operation B was verysatisfactory in that it contained only 4% by volume of oil.

What is claimed is:

Improved process for segregation of more aromatic type constituents frommore parafiinic type constituents of a petroleum oil, which comprisesintroducing said petroleum oil into the bottom of a countercurrenttreating zone, introducing substantially pure phenol into the top ofsaid countercurrent treating zone, maintaining conditions in said zoneto secure a raflinate phase and a solvent extract phase having an oilcontent of less than about 8%, separating said solvent extract phase andchilling the same to a temperature below the crystallization temperatureof phenol to crystallize a substantial proportion of the phenol contentthereof, removing phenol crystalsfrom said solvent extract phase,subjecting the same to pressure in excess of about pounds per squareinch and removing oil therefrom, reheating said pressed crystals andrecycling said phenol to said treating zone at a point below the pointof introduction of said substantially pure phenol, and subjecting saidsolvent extract phase from which said crystals have been removed to adistillation zone wherein substantially pure phenol is separated fromsaid extract and recycled to the top of said treating zone.

References Cited in the file of this patent UNITED STATES PATENTS1,779,287 Pfafi et al. Oct. 21, 1930 1,820,645 Bennett Aug. 25, 19312,216,933 Atkins Oct. 8, 1940 2,557,406 Blazer et al. June 19, 1951OTHER REFERENCES Norris: Experimental Organic Chem., 2nd Ed. (1924),pages 7 and 8, McGraw-Hill, 330 W. 42nd Street, New York, N. Y.

